Chemical process is an important Enhanced Oil Recovery technology for intensified oil production, and the chemical flooding is one of the most effective and potential measures, which is especially represented by polymer flooding. However, there arise some problems in the polymer system for conventional flooding with the deep implementation of polymer flooding technology. Under reservoir conditions of high temperature and high salinity, the viscosifying capacity and thermal stability of the widely used partially hydrolyzed polyacrylamide polymer reduces rapidly; in the meantime, the polyacrylamide polymer does not have the surface/interfacial reactivity per se, and could not start the oil film effectively, so that its ability to mine the remaining oil is limited. The polymer-based binary-component composite system (polymer/surfactant) and triple-component system (polymer/surfactant/alkali) may enhance the emulsification stability of the crude oil produced fluid, resulting in increased difficulty in oil/water separation and sewage treatment, as well as the weakening of synergistic effect between the components of the system under reservoir conditions, and also it may damage the reservoir. The application of the composite system is thus restricted.
Heavy oil recovery is a common difficulty around the world, mainly because the heavy oil is high in viscosity, high in gum asphaltene content or wax content, thus, the heavy oil is does not easily flow in the formation, wellbore and oil pipeline. Furthermore, since the oil-water mobility ratio is big, it can easily cause many problems such as rapid water breakthrough, high water content of produced fluid, and easy formation sand production. The process for heavy oil recovery can be mainly divided into recovery of liquid flooding (e.g., hot water flooding, steam huff and puff, steam flood and so on) and recovery of yield enhancement (e.g., horizontal well, compositing branched well, electric heating and etc). A Chemical viscosity reducer can disperse and emulsify the heavy oil effectively, reduces the viscosity of the heavy oil remarkably and decreases the flow resistance on heavy oil in the formation and wellbore, which is significantly important for reducing energy consumption in the process of recovery, decreasing discharging pollution and enhancing heavy oil recovery.